There is a longstanding misconception that dogs are colorblind and perceive the world in grayscale, like some monochrome television set from the 1940s. Further it is has been believed that since a dog is colorblind, it uses the level of brightness to distinguish between objects. In the context of recent researchers, it is clear that humans have been barking up the wrong tree.
In the 1980s, neurobiologist and vision expert Jay Neitz and his team of researchers at the University of California, Santa Barbara and later at the University of Washington conducted experiments that demonstrated that dogs actually see in color. Eyes contain light-sensitive cells, called cones, that respond to color. The eyes of some animals, like a certain species of shrimp, contain twelve types of cones; other animals, like birds and fish, have four types of cones; humans and most primates have three types of cones (red, green, blue), while dogs have two types of cones (blue, yellow). With three cones (trichromacy), the human eye sees the full range of the spectrum (red, orange, yellow, green, blue, indigo, and violet) and distinguish up to 2 million colors. Since a dog’s eye contains only two cones (dichromacy), it cannot see that full range of color — only the blue-yellow range — and the ability to distinguish 1 million colors. If you view the blue-yellow spectrum, on the far left, it starts with a brownish gold that fades to light yellow, followed by a middle band of gray, followed by successively darker bands of blue (cyan to deep blue). Humans with mutations on the X chromosome are born colorblind (referred to red-green color blind, since they cannot see reds and greens), and thus have the very same color capacity as a dog. For example, when viewing a group of red apples, a dog or colorblind human sees the apples in slightly different shades of dark yellow (a sort of yellowish-gray).
Building on the research of Neitz and his colleagues, Anna Kasparson and a her team at the Laboratory of Sensory Processing at the Russian Academy of Sciences conducted additional experiments in 2013 to test canine color vision. Specifically, the researchers wanted to answer the question: do dogs use color vision or levels of brightness to identify objects? The experiments proved that dogs rely more on color than on brightness to distinguish between objects. The researchers wrote: “[We] show that for eight previously untrained dogs, color proved to be more informative than brightness when choosing between visual stimuli differing both in brightness and chromaticity. Although brightness could have been used by the dogs in our experiments, it was not. Our results demonstrate that under natural photopic lighting conditions color information may be predominant even for animals that possess only two spectral types of cone photoreceptors.”
So next time you play fetch with Fido, consider that the red or orange ball you are tossing in the lawn is not so visually obvious to him as it is to you. For Fido, the red ball appears brownish-yellow against grass that is also appears brownish-yellow. It’s a good thing your beloved pet can smell it better than he can see it.
For further reading: philly.com/philly/blogs/evolution/How-Dogs-See-the-World-The-Evolutionary-Story-of-Color-Vision.html?c=r